Does it not have a recovery partion - What is the model ?

Try this

  1. Copy all your files and documents to an external storage device. Using Reatogo
  2. Shut down the computer.
  3. Turn the PC back on and hit the F8 key repeatedly until the Advanced Boot Option Screen appears.
  4. Click “Repair Your Computer” if you are not already on it and then press ENTER
  5. choose your country and click OK
  6. On the “System Recovery Options Screen” click “Restore Application” which is the last option.
  7. Follow the on-screen instructions
  8. When prompted, click on “Full Factory Recovery”
  9. “Next”
  10. Click “Yes”
  11. you will notice for a while it seems like nothing is happening, give it some time.
  12. After some minutes, recovery will complete and you click “Finish”

Or this

  1. Press and hold the 0 (zero) key and at the same time, tap the power button once to switch on your notebook.
  2. When the machine Starts beeping; release the 0 key.
  3. When prompted by the warning screen; select Yes to continue with the system recovery.
  4. Select Recovery of Factory Default Software; click Next.
  5. Select Recover to out-of-box state. Click Next again.
  6. Click Next to Start recovery.